Scientists Use Seals to Videotape Deep Sea Fish

Jan. 31

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The scientists ended up with nearly 200 hours of videotape, most of it black because the cameras ran continuously as the seals prowled through the deeper waters. But every now and then, a flash appeared in the darkness. By examining that flash, frame by frame, the researchers were able to tell if the flash was a silverfish, a six to eight inch long fish that nearly everybody eats in Antarctica, or a toothfish, a big fish that can range up to six feet long.

The images are not "TV quality," Fuiman says, because there's so little light available that only black and white images could be acquired. But they served the essential function of letting the researchers know exactly what kind of prey the seals were after.

The data revealed a few surprises. Both species, which are critical components in Antarctica's food chain, roam over widely ranging depths. Silverfish, for example, were found as deep as 1,132 feet.

Independent Researchers

One of the questions confronting the scientists is how the seals track down their prey, and there was at least one clue in the data. Some scientists believe seals can smell their prey, and even follow that scent through the water, and others think the seals probably use sight.
"You and I are very visual organisms, and our first guess is that they are using sight," Fuiman says. "I'm not quite ready to jump to that conclusion yet."

However, the videotape shows that in a number of instances, the seals came up from below to attack the silverfish, suggesting that light penetrating through the ice above may have allowed them to see the prey.

That's one of the questions that the researchers hope to answer in the current phase of the project. Emboldened by their success, the scientists abandoned their hole-in-the-ice approach and began strapping their equipment on seals found in their natural environment. It was a bit risky, because there was no guarantee that they would be able to find the seal later, but it would allow the seals to interact with other seals.

And it all worked out. All of the seals returned to the area, so the scientists could recover their data.

That included Ally McSeal, who perhaps should have been named McPig, because she was seen slurping down at least 100 silverfish during a single dive.

And when it was all over, McSeal "returned repeatedly" to a group of scientists who had set up camp on the pack ice, according to Williams.

Maybe she just wanted to get screen credits.

Lee Dye’s column appears weekly on ABCNEWS.com. A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.